1. Field of the Invention
The present invention pertains to the deflection of beams of charged particles and, more particularly, to a system for deflecting a scanning beam of charged particles to uniformly irradiate hollow objects.
2. Discussion of the Prior Art
High energy charged particle beams, such as high energy electron beams, are usually required to be scanned for use in industrial processes in order to spread the beam uniformly over a wide conveyor path; and, frequently, it is also required to modify the direction or shape of the beam to conform to the shape or orientation of the object to be irradiated. To acccomplish this, the prior art has utilized various combinations of beam scanning and bending magnets.
Beam scanning and bending systems can generally be classified in two categories dependent upon whether the beam is scanned before or after bending. Scanning after bending is normally utilized if the beam is to be transported some distance, such as from one room to another, or if there is sufficient space for a conventional beam scanning device between the bending magnet and a conveyor path along which the object to be irradiated is travelling. Bending after scanning is utilized where the space between the bending magnet and the object to be irradiated is inadequate for a conventional scanning system, and where the shape of the scanning beam must be distorted to impinge on the object to be irradiated from several different directions. Prior art scanning and bending systems have had the disadvantages of undesirably modifying other properties of the beam, such as divergence and uniformity, singly or collectively, thereby causing the resulting irradiating beam to produce non-uniform irradiation.
The prior art, as exemplified by U.S. Pat. Nos. 2,824,969 to Crowley-Milling, 2,887,583 to Emanuelson, 2,892,946 to Dewey II et al, 2,897,365 to Dewey II et al, 2,993,120 to Emanuelson, 3,013,154 to Trump, 3,094,474 to Gale, 3,104,321 to Smith, Jr., 3,379,911 to Enge, 3,833,814 to Nablo, 3,867,635 to Brown et al, 3,956,634 to Tran et al and 4,075,496 to Uehara, is cognizant of the bending of a scanning beam and, separately, the bending or deflection of a beam 270.degree. prior to scanning, however, the prior art has failed to produce apparatus for bending a beam of charged particles after scanning in a manner so as to produce uniform irradiation without adversely modifying other properties of the beam.